Accounts Receivable (Details) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Accounts Receivable
Premiums receivable	$ 46,974,000	$ 39,084,000
Other receivables	3,166,000	1,571,000
Total accounts receivable	50,140,000	40,655,000
Less: Allowance for doubtful accounts	0	0
Accounts receivable, net	50,140,000	40,655,000
Provision for doubtful accounts	$ 0	$ 0	$ 0
Premiums receivable
Accounts Receivable
Threshold period unpaid for write-off of mortgage insurance premiums (more than)	90 days